HFU HF Underground

General Category => General Radio Discussion => Topic started by: MDK2 on May 21, 2017, 2008 UTC

Title: Question about images that are sent in radio transmissions
Post by: MDK2 on May 21, 2017, 2008 UTC: I don't mean SSTV. I'm speaking of the images that some pirates have recent started sending that can be seen in the waterfall displays of those using SDR's.

I like tuning into the VOA radiogram, and they send images of the VOA and Radiogram logos. I've only ever been able to see those in the waterfall display of Fldigi, however, not SDRuno. I don't know if this is due to my settings, the software itself, or something else. And so far I haven't observed any of the images that some pirates like Burn It Down Radio, Radio Time, and Pee Wee have recently sent to identify themselves or to give shout-outs to HFU listeners. Timing and the typically fair-to-poor signal strength are doubtless factors, but I'd like to know what I need to do to see these if I'm lucky enough to be viewing the waterfall when they send something, or playing back a SDR recording. (Would they appear in Fldigi's waterfall if I had that up and running?)

Thanks for your help.
Title: Re: Question about images that are sent in radio transmissions
Post by: ChrisSmolinski on May 21, 2017, 2015 UTC: These images the pirate stations are sending would be viewable in the waterfall of your SDR app, or possibly in the waterfall of a digital app, if you are tuned in SSB mode, and the bandwidth is wide enough. I've been able to view them by playing back an SDR recording, and fast forwarding to the appropriate time.
Title: Re: Question about images that are sent in radio transmissions
Post by: MDK2 on May 21, 2017, 2027 UTC: Does the contrast need to be high, or are they fairly visible regardless of that setting?
Title: Re: Question about images that are sent in radio transmissions
Post by: ChrisSmolinski on May 21, 2017, 2039 UTC: Quote from: MDK2 on May 21, 2017, 2027 UTC
Does the contrast need to be high, or are they fairly visible regardless of that setting?

I had to fiddle with the settings a few times to get a reasonable image.
Title: Re: Question about images that are sent in radio transmissions
Post by: MDK2 on May 21, 2017, 2129 UTC: Kewl. Thanks Chris!
Title: Re: Question about images that are sent in radio transmissions
Post by: refmo on May 22, 2017, 0019 UTC: Also, the speed of your waterfall is very important to how the image will look.
If your waterfall is moving very slowly, the image may be too compressed vertically to see anything.
Or if the waterfall is moving very quickly, the image may expand too much to fit on your display.
Title: Re: Question about images that are sent in radio transmissions
Post by: Stretchyman on May 23, 2017, 0558 UTC: Fairly simple to use EASYPAL. However the B/W is restricted to 3KHz, which is a pain got Tx. Anyone know how to W-I-D-E-N it?
Title: Re: Question about images that are sent in radio transmissions
Post by: ChrisSmolinski on May 23, 2017, 1227 UTC: If you've got an iPad or iPhone, my Godafoss waterfall app can be used: http://www.blackcatsystems.com/ipad-iphone-ipod-touch-shortwave-ham-amateur-radio-app/godafoss-audio-spectrum-waterfall-qrss-cw-dfcw-fsk-cw-decoder.html
Title: Re: Question about images that are sent in radio transmissions
Post by: Josh on May 23, 2017, 1716 UTC: As easypal is set for a nominal 3khz bw for the mode it runs (drm is a derivative of STANAG4285 = 2.4KHz wide) I don't think you can alter the waterfall where it shows the callsigns and other messages other than to make it run upwards or downwards.
Title: Re: Question about images that are sent in radio transmissions
Post by: Stretchyman on May 23, 2017, 1819 UTC: Dont have an iPhone, and shame the B/W is restricted, ah well, just a bit of harmless fun anyways.....

Str.